Decided "cow" is not irregular; strong stem *gʷow generalized, and Brugmann's + Szerémenyi's yielded a uniform stem ⲕⲟⲩ-.

"Water" (ⲡⲟⲩⲧⲉⲣ) shows an irregular singular paradigm. The nom./acc./voc. shows the reflex of *wódṛ; elsewhere the oblique stem *uden- appears.

nom.	ⲡⲟⲩⲧⲉⲣ
gen.	ⲟⲧⲉⲥ
dat.	ⲟⲧⲓⲛⲉ
ins.	ⲟⲧⲓⲛⲙⲓ
loc.	ⲟⲧⲓⲛⲓ

'Earth' shows a highly irregular paradigm. Note that the instrumental continues the original *ǵʰmeh₁ and adds the usual *-mi.

nom.	ⲅⲇⲟⲩⲛ
gen.	ⲅⲙ-ⲓⲥ
acc.	ⲅⲇⲟⲩⲛ-ⲉⲛ
dat.	ⲅⲙ-ⲉ
ins.	ⲅⲙ-ⲉⲙⲓ
loc.	ⲅⲙ-ⲓ
voc.	ⲅⲇⲟⲛ

Other archaic paradigms mostly got levelled out, e.g. ⲫⲟⲣ 'fire' is an unexceptional neuter consonant stem,